Science Says Blowing Out Birthday Candles Is Gross

Mmm, birthday bacteria.


Birth is a bacterial-laden affair; how could sliding through the vaginal canal not be? So it’s fitting that every subsequent birthday is dripping with microorganisms, too, thanks to the spit strewn over every cake as the wishes are made and the candles blown out.

A study published in the Journal of Food Research reveals just how much: Researchers at Clemson University in South Carolina documented a 1,400 percent increase in the bacteria load on birthday cakes in the moments following the sacred blow.

Though covering your guest’s slices of cake in spittle is definitely a party foul, scientists say, safety-wise, there’s no reason to be a party pooper and forgo the dirty dessert.

To test the germ-y residue left on a birthday cake, food safety professor Paul Dawson and his team concocted a fake cake. A base made of styrofoam, wrapped in tinfoil, and covered in icing, the cake had 17 candles poked into it. “Each test subject was asked to smell and consume a piece of hot pizza to simulate a meal-dessert sequence,” the study says, before extinguishing all 17 candles with a gust or three.

Dawson and his team found that the icing samples that received the “blow treatment,” as the study called it, had an average 1,400 percent increase in bacterial load over icing samples that had received the “no blow treatment.” But the amount of bacteria on the infected icing ranged wildly, with one participant dispersing a truly delivering 120,000 the bacteria to their cake as compared to the “no blow” cake.

Still, Dawson says, even the friends of the blower batting 120,000 don’t have to be too worried. For starters, mouth bacteria isn’t all that bad. If you’re battling an infection, you might want to keep it to yourself, but on the whole it’s pretty neutral. And if you come into contact with someone else’s spittle, your own saliva would probably protect you. Kind of like the water in a toilet, our saliva’s main job is to flush out invaders and send dangerous microorganisms flowing down spit river and into your acid bath of a stomach. Lysozome, histatin, and other microbial-busting molecules live in our mouths and also help keep things clean.

What’s more, Dawson says, even the highest end of the birthday cake spray probably wouldn’t carry enough dangerous bacteria to make you sick. “It’s not a big health concern in my perspective,” he told The Atlantic. “In reality if you did this 100,000 times, then the chance of getting sick would probably be very minimal.”

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